1. Field of the Invention
The present invention relates to a system and a method for an auto-ignition of gasoline internal combustion engine that runs under lean burn and controlled auto-ignition combustion conditions during operation with part load.
2. Description of Related Art
To improve thermal efficiency of gasoline internal combustion engines, lean burn is known to give enhanced thermal efficiency by reducing pumping losses and increasing ratio of specific heats. Flatly speaking, lean burn is known to give low fuel consumption and low NOx emissions. There is however a limit at which an engine can be operated with a lean air/fuel mixture because of misfire and combustion instability as a result of a slow burn. Known methods to extend the lean limit include improving ignitability of the mixture by enhancing the fuel preparation, for example using atomized fuel or vaporized fuel, and increasing the flame speed by introducing charge motion and turbulence in the air/fuel mixture. Finally, combustion by auto-ignition has been proposed for operating an engine with very lean air/fuel mixtures.
When certain conditions are met within a homogeneous charge of lean air/fuel mixture during low load operation, auto-ignition can occur wherein bulk combustion takes place initiated simultaneously from many ignition sites within the charge, resulting in very stable power output, very clean combustion and high thermal efficiency. NOx emission produced in controlled auto-ignition combustion is extremely low in comparison with spark ignition combustion based on propagating flame front and heterogeneous charge compression ignition combustion based on an attached diffusion flame. In the latter two cases represented by spark ignition engine and diesel engine, respectively, the burnt gas temperature is highly heterogeneous within the charge with very high local temperature values creating high NOx emission. By contrast, in controlled auto-ignition combustion where the combustion is uniformly distributed throughout the charge from many ignition sites, the burnt gas temperature is substantially homogeneous with much lower local temperature values resulting in very low NOx emission.
Engines operating under controlled auto-ignition combustion have already been successfully demonstrated in two-stroke gasoline engines using a conventional compression ratio. It is believed that the high proportion of burnt gases remaining from the previous cycle, i.e., the residual content, within the two-stroke engine combustion chamber is responsible for providing the hot charge temperature and active fuel radicals necessary to promote auto-ignition in a very lean air/fuel mixture. In four-stroke engines, because the residual content is low, auto-ignition is more difficult to achieve, but can be induced by heating the intake air to a high temperature or by significantly increasing the compression ratio.
In all the above cases, the range of engine speeds and loads in which controlled auto-ignition combustion can be achieved is relatively narrow. The fuel used also has a significant effect on the operating range, for example, diesel fuel and methanol fuel have wider auto-ignition ranges than gasoline fuel.
An auto-ignition, which is induced by heating fuel and significantly increasing the compression ratio, in four-stroke gasoline engine is described in U.S. Pat. No. 5,535,716, which claims priority of Japanese patent application No. 6-150487 that was laid open as JP-A 7-332141 on Dec. 22, 1995. Gasoline fuel is injected inside the intake port a considerable amount of time before the intake valve is open so that the mixture of air and gasoline in the intake port is sufficiently heated before entering the combustion chamber. The mixture is ignited by compression ignition performed at high pressure. Since the gasoline fuel injected in the intake port is completely evaporated before entering the combustion chamber, reliable compression ignition is achieved. The compression ratio ranges from about 14 to about 20. Use of a compression ratio of 17.7 is described as the most preferred implementation in this publication. Injection of the gasoline fuel is performed during a predetermined period from 10 degrees of crankshaft angle before the intake valve is closed to 110 degrees of crankshaft angle before the intake valve is opened.
JP-A 11-72038 describes a technique to avoid knocking in a compression ignition diesel engine. According to this known technique, an amount of diesel fuel less as much as 30 percent of the maximum amount of fuel is injected during a period from about 90 degrees of crankshaft angle before top dead center (TDC) of compression stroke to about 20 degrees of crankshaft angle before the TDC. This first injection of diesel accomplishes sufficient oxidation of fuel by the time the piston ascends to TDC of the compression stroke. At around the TDC, a second injection of diesel is performed to initiate burning of the injected diesel. This knocking avoidance technique cannot be applied to compression ignition of gasoline fuel that has a low cetane number.
The present invention seeks to provide a system and a method for operating an internal combustion engine such that lean burn of gasoline fuel due to controlled auto-ignition takes over the engine operation over an extended range of an engine operation parameter indicative of the engine speed or the engine load.
An object of the present invention is to provide a system and a method for an auto-ignition of gasoline internal combustion engine such that parameters controlling the cylinder content including gasoline fuel are adjusted to cause an auto-ignition over an extended range of an engine operation parameter.
Another object of the present invention is to provide a computer readable storage device or medium for a system and a method for an auto-ignition of gasoline internal combustion engine such that parameters controlling the cylinder content including gasoline fuel are adjusted to cause an auto-ignition over an extended range of an engine operation parameter.
In carrying out the present invention, a system for an auto-ignition of gasoline internal combustion engine is provided. The system comprises:
a cylinder;
a piston disposed within said cylinder for reciprocating motion to define a combustion chamber;
intake means for admitting fresh air into said cylinder;
a fuel injector directly communicating with said combustion chamber;
exhaust means for discharging exhaust gas resulting from combustion within said cylinder; and
a control unit adjusting opening and closing timings of said intake means and opening and closing timings of said exhaust means such that said piston reciprocates within said cylinder to perform an exhaust phase, an exhaust gas retaining phase, an intake phase, a compression phase, and an expansion phase, wherein said intake means and exhaust means being closed to retain exhaust gas within said cylinder during said exhaust gas retaining phase,
said control unit providing a first start time of a first fuel injection by said fuel injector during said exhaust gas retaining phase and a second start time of a second fuel injection by said fuel injector during said compression phase,
said control unit determining a portion of total fuel quantity and the remainder of said total fuel quantity,
said control unit determining a first fuel injection control signal indicative of said portion of said total fuel quantity and applying said first fuel injection control signal to said fuel injector at said first start time to control fuel quantity injected for said first fuel injection,
said control unit determining a second fuel injection control signal indicative of the remainder of said total fuel quantity and applying said second fuel injection control signal at said second start time to control fuel quantity injected for said second fuel injection,
said remainder of said total fuel quantity being proportional to the engine load of the internal combustion engine.
In carrying out the present invention, one embodiment provides a system for an auto-ignition of gasoline internal combustion engine comprising:
a cylinder;
a piston disposed within said cylinder for reciprocating motion to define a combustion chamber;
intake means for admitting fresh air into said cylinder;
a fuel injector directly communicating with said combustion chamber;
exhaust means for discharging exhaust gas resulting from combustion within said cylinder; and
a control unit selecting one of a gasoline reform auto-ignition combustion mode and an auto-ignition combustion mode in response to magnitude of an operating parameter indicative of one of the engine load and the engine speed of the internal combustion engine,
said control unit being operative during selection of said gasoline reform auto-ignition combustion mode to adjust opening and closing timings of said intake means and opening and closing timings of said exhaust means such that said piston reciprocates within said cylinder to perform an exhaust phase, an exhaust gas retaining phase, an intake phase, a compression phase, and an expansion phase,
said control unit being operative during selection of said gasoline reform auto-ignition combustion mode to provide a first start time of a first fuel injection by said fuel injector during said exhaust gas retaining phase and a second start time of a second fuel injection by said fuel injector during said compression phase,
said control unit determining total fuel quantity to be injected in response to engine load of the internal combustion engine,
said control unit being operative during selection of said gasoline reform auto-ignition combustion mode to determine a portion of and the remainder of said determined total fuel quantity,
said control unit being operative during selection of said gasoline reform auto-ignition combustion mode to determine a first fuel injection control signal indicative of said portion of said determined total fuel quantity and applying said first fuel injection control signal to said fuel injector at said first start time to control fuel quantity injected for said first fuel injection,
said control unit being operative during selection of said gasoline reform auto-ignition combustion mode to determine a second fuel injection control signal indicative of the remainder of said determined total fuel quantity and applying said second fuel injection control signal at said second start time to control fuel quantity injected for said second fuel injection.
In carrying out the present invention, a computer readable storage device is provided. The computer readable storage device has stored therein data representing instructions executable by a computer to implement an auto-ignition of gasoline internal combustion engine. The engine has a piston disposed in a cylinder for reciprocating motion to define a combustion chamber, intake means for admitting fresh air into the cylinder, a fuel injector directly communicating with the combustion chamber, and exhaust means for discharging exhaust gas resulting from combustion within the cylinder, wherein opening and closing timings of the intake means and opening and closing timings of the exhaust means are adjustable. The computer readable storage device comprises:
instructions for adjusting opening and closing timings of the intake means and opening and closing timings of the exhaust means such that the piston reciprocates within the cylinder to perform an exhaust phase, an exhaust gas retaining phase, an intake phase, a compression phase, and an expansion phase;
instructions for providing a first start time of a first fuel injection by the fuel injector during said exhaust gas retaining phase and a second start time of a second fuel injection by the fuel injector during said compression phase;
instructions for determining a portion of total fuel quantity and the remainder of said total fuel quantity;
instructions for determining a first fuel injection control signal indicative of said portion of said total fuel quantity and applying said first fuel injection control signal to the fuel injector at said first start time to control fuel quantity injected for said first fuel injection; and
instructions for determining a second fuel injection control signal indicative of the remainder of said total fuel quantity and applying said second fuel injection control signal to the fuel injector at said second start time to control fuel quantity injected for said second fuel injection.
In carrying out the present invention, there is further provided a computer readable storage device having stored therein data representing instructions executable by a computer to implement an auto-ignition of gasoline internal combustion engine, the engine having a piston disposed in a cylinder for reciprocating motion to define a combustion chamber, intake means for admitting fresh air into the cylinder, a fuel injector directly communicating with the combustion chamber, and exhaust means for discharging exhaust gas resulting from combustion within the cylinder, wherein opening and closing timings of the intake means and opening and closing timings of the exhaust means are adjustable, the computer readable storage device comprising:
instructions for selecting one of a gasoline reform auto-ignition combustion mode and an auto-ignition combustion mode in response to magnitude of an operating parameter indicative of one of the engine load and the engine speed of the internal combustion engine;
instructions for adjusting, during selection of said gasoline reform auto-ignition combustion mode, opening and closing timings of the intake means and opening and closing timings of the exhaust means such that the piston reciprocates within the cylinder to perform an exhaust phase, an exhaust gas retaining phase, an intake phase, a compression phase, and an expansion phase;
instructions for providing, during selection of said gasoline reform auto-ignition combustion mode, a first start time of a first fuel injection by the fuel injector during said exhaust gas retaining phase and a second start time of a second fuel injection by the fuel injector during said compression phase;
instructions for determining total fuel quantity to be injected in response to engine load of the internal combustion engine;
instructions for determining, during selection of said gasoline reform auto-ignition combustion mode, a portion of and the remainder of said determined total fuel quantity;
instructions for determining, during selection of said gasoline reform auto-ignition combustion mode, a first fuel injection control signal indicative of said portion of said determined total fuel quantity and applying said first fuel injection control signal to the fuel injector at said first start time to control fuel quantity injected for said first fuel injection; and
instructions for determining, during selection of said gasoline reform auto-ignition combustion mode, a second fuel injection control signal indicative of the remainder of said determined total fuel quantity and applying said second fuel injection control signal to the fuel injector at said second start time to control fuel quantity injected for said second fuel injection.
In carrying out the present invention, there is provided a method for an auto-ignition of gasoline internal combustion engine, the engine having a piston disposed in a cylinder for reciprocating motion to define a combustion chamber, intake means for admitting fresh air into the cylinder, a fuel injector directly communicating with the combustion chamber, and exhaust means for discharging exhaust gas resulting from combustion within the cylinder, wherein opening and closing timings of the intake means and opening and closing timings of the exhaust means are adjustable, the method comprising:
adjusting opening and closing timings of the intake means and opening and closing timings of the exhaust means such that the piston reciprocates within the cylinder to perform an exhaust phase, an exhaust gas retaining phase, an intake phase, a compression phase, and an expansion phase;
providing a first start time of a first fuel injection by the fuel injector during said exhaust gas retaining phase and a second start time of a second fuel injection by the fuel injector during said compression phase;
determining a portion of total fuel quantity and the remainder of said total fuel quantity;
determining a first fuel injection control signal indicative of said portion of said total fuel quantity;
determining a second fuel injection control signal indicative of the remainder of said total fuel quantity;
applying said first fuel injection control signal to the fuel injector at said first start time to control fuel quantity injected for said first fuel injection; and
applying said second fuel injection control signal at said second start time to control fuel quantity injected for said second fuel injection.
In carrying out the present invention, there is provided a method for an auto-ignition of gasoline internal combustion engine, the engine having a piston disposed in a cylinder for reciprocating motion to define a combustion chamber, intake means for admitting fresh air into the cylinder, a fuel injector directly communicating with the combustion chamber, and exhaust means for discharging exhaust gas resulting from combustion within the cylinder, wherein opening and closing timings of the intake means and opening and closing timings of the exhaust means are adjustable, the method comprising:
selecting one of a gasoline reform auto-ignition combustion mode and an auto-ignition combustion mode in response to magnitude of an operating parameter indicative of one of the engine load and the engine speed of the internal combustion engine;
adjusting, during selection of said gasoline reform auto-ignition combustion mode, opening and closing timings of the intake means and opening and closing timings of the exhaust means such that the piston reciprocates within the cylinder to perform an exhaust phase, an exhaust gas retaining phase, an intake phase, a compression phase, and an expansion phase;
providing, during selection of said gasoline reform auto-ignition combustion mode, a first start time of a first fuel injection by the fuel injector during said exhaust gas retaining phase and a second start time of a second fuel injection by the fuel injector during said compression phase;
determining total fuel quantity to be injected in response to the engine load of the internal combustion engine;
determining, during selection of said gasoline reform auto-ignition combustion mode, a portion of and the remainder of said determined total fuel quantity;
determining, during selection of said gasoline reform auto-ignition combustion mode, a first fuel injection control signal indicative of said portion of said determined total fuel quantity;
determining, during selection of said gasoline reform auto-ignition combustion mode, a second fuel injection control signal indicative of the remainder of said determined total fuel quantity;
applying said first fuel injection control signal to the fuel injector at said first start time to control fuel quantity injected for said first fuel injection; and
applying said second fuel injection control signal to the fuel injector at said second start time to control fuel quantity injected for said second fuel injection.